The present invention relates to a method of preparing pyrazole compounds of the following formula (I): ##STR3## wherein R is an optionally substituted alkyl group, and optionally substituted aryl group or an optionally substituted heterocyclic group.
The compounds of formula (I) are useful as intermediates in the preparation of pyrazolotriazole dye-forming couplers employed in photographic silver halide materials, For example, a typical coupler can be represented by the general formula (II): ##STR4## wherein R.sup.2 is a substituent know in the photographic art; X is hydrogen or a coupling-off group known in the photographic art; and Z.sup.a, Z.sup.b and Z.sup.c are independently a substituted or unsubstituted methine group, .dbd.N-, .dbd.C- or -NH-, provided that one of either the Z.sup.a --Z.sup.b bond or the Z.sup.b --Z.sup.c bond is a double bond and the other is a single bond, and when the Z.sup.b --Z.sup.c bond is a carbon--carbon double bond, it may form part of an aromatic ring, and at least one of Z.sup.a, Z.sup.B and Z.sup.c represents a methine group connect with the group R.sup.2.
One class of pyrazolotriazole couplers includes 1H-pyrazolo[1,5b][1,2,4]triazole couplers, such as described in European Patent 1777765. These couplers can be represented by the general formula: ##STR5## wherein R and R.sup.2 are as defined above.
Another class of pyrazolotriazole couplers include 1H-pyrazol [3,2-]-5-triazole couplers, such as described in U.S. Pat. Nos. 3,725,067 and 4,812,576. These couplers can be represented by the general formula: ##STR6## wherein R and R.sup.2 are as defined above.
The intermediate compounds of formula (I) can be used to form pyrazolotriazole couplers according to methods known in the art. Such methods are disclosed in U.S. Pat. Nos. 4,540,654 and 4,812,576.
The method according to the presently claimed method has the advantage that the starting materials are commercially available. Additionally, the reagents pose no significant health or disposal risks. The method avoids the use of reagents which, if present as residual materials, would be undesirable in further processing of photographic elements.